Refinery acid sludges were created when crude oils and lubricating oil precursors were contacted with high concentrations of sulfuric acid to extract sulfur, oxygen and nitrogen-containing constituents that would otherwise be unstable. Air may have been bubbled through the acid-petroleum mixture and a precipitate formed. This process was prevalent some 30-40 years ago. Such precipitates, i.e., acid sludges, were for some years disposed of in surface impoundments (pits). The aged acid sludge is a tarry mass which must now be removed from the disposal site and permanently disposed of or recycled. One method of disposal of oily waste is claimed in copending application Ser. No. 379,408, filed July 12, 1989, by P. S. Sundar. In the Sundar process, which is not adapted to acid waste, one adds solids and a binder, such as portland cement to an oily waste to form granules. The purpose of the Sundar process is not neutralization of the oily waste which is substantially neutral to begin with. The granules are contacted with a solvent to obtain a solvent-granules mix. A solvent-hydrocarbon phase is then separated from the solvent-granules mixture by solvent extraction. Limestone is a preferred solid added to oily waste in Sundar's process as an inert or substantially inert absorbent material. Other fillers may be used in place of limestone in the Sundar process, such as, fly ash, catalyst fines, etc. Methyl ethyl ketone is disclosed to be a solvent for that granulated solid process. A preferred method of Sundar's process contacts the granular mass with the solvent in a multi stage countercurrent flow in which the granular mass travels in one direction and the solvent travels in another. The direct neutralization of acid sludge with a solid base, such as limestone, is not possible because of the semi-solid tarry nature of the acid sludge. Furthermore, the treatment of acid sludge with base, such as limestone, produces substantial amounts of heat and gas while the treatment of a substantially neutral oil waste does not.
ASTM Test Method D94 determines the amount of constituents in a petroleum product that will saponify under conditions of the test. In this test a known weight of the sample is dissolved in methyl ethyl ketone (MEK) and is heated with a known amount of KOH. The excess alkali is titrated with acid and the saponification number of the sample calculated. Vapors from this method can cause flash fires.
U.S. Pat. Nos. 4,073,719 and 4,073,720 discloses the refining of used waste lubricating oil and crankcase oils by vacuum distillation to strip water and volatiles, mixing the stripped oil with a solvent comprising alcohol and methyl ethyl ketone to precipitate a sludge, separating the sludge to recover a partially purified oil, and separating the oil from the solvent before vacuum-distilling the oil. U.S. Pat. No. 4,152,528 discloses a process for extracting phenol from a phenol-water mixture using methyl ethyl ketone as a component of the extracting medium. U.S. Pat. No. 3,929,586 discloses a process for removing organic solvents from solvent-containing waste sludges by mixing said sludge with an alkali or alkaline earth base to form a mixture of pH greater than 7 from which the solvent is distilled. Such solvents include methyl ethyl ketone. U.S. Pat. No. 4,801,384 discloses a process for decontamination of sludges contaminated with organic materials by leaching the solid sludge with a leaching solvent, and stripping the organic material from the leaching solvent with a stripping solvent. Such contaminants include polynuclear aromatics, and such leaching solvents include methyl ethyl ketone.
It would be advantageous if tarry acid sludge could be efficiently neutralized. It would be more advantageous if by some process the substantial hydrocarbon content of acid sludge could be recovered for subsequent use, for example, as a component of asphalt. It would be especially advantageous if the solid product of such a process were "delistable", i.e., not on any State or Federal Environmental Protection Agency list of toxic materials. In order to be delistable, the concentration of toxic materials, such as polynuclear aromatics, must be reduced in the product solid to a very low level.